In conventional process for optical fiber fabrication, to protect the surface of an optical fiber pulled out as a string and maintain the strength of the optical fiber, an ultraviolet curable coating agent is coated on the surface of the optical fiber. The coating agent is coated in uncured state by a coating apparatus, and is cured by a light illuminating apparatus that performs ultraviolet light irradiation (for example, Patent Literature 1).
Patent Literature 1 discloses an apparatus that allows an optical fiber pulled out as a string coated with a coating material (a coating agent) to pass through a curing chamber with an elliptical housing so as to cure the coating material. Inside the elliptical housing, an elliptical mirror, and a quartz halogen lamp extending parallel to the path of the optical fiber are installed, and the quartz halogen lamp and the optical fiber are respectively positioned at a first focal point and a second focal point of the elliptical mirror, to make sure that ultraviolet light irradiated from the quartz halogen lamp reaches the outer periphery of the optical fiber.